摘要:
Multinuclear (i.e. H-1 C-13 and Pt-195) NMR spectra of six platinum(IV) porphyrin complexes are reported. Compared with their platinum (II) porphyrin precursors, alphacarbon (C-alpha) resonances are shifted further upfield, H-1-Pt-195 and C-13-(195)pt coupling constants are significantly reduced, Pt-195 resonances are shifted further downfield (their relative positions being more strongly affected by macrocyclic substitution) and (195)pt peaks are appreciably narrowed. These differences are rationalized in terms of oxidation leading to reduced coupling of (195)pt to the N-14 C-13 and H-1 atoms of the porphyrin, a slight increase in d-pi(*) back-bonding and its modulation by porphyrin substituents.